1. Field of the Invention
The present invention relates generally to force sensors and, more particularly, to a force sensor that disposes a piezoelectric component between a wall within a cavity formed in a first member and a second member disposed within the cavity and slideably associated therewith.
2. Description of the Prior Art
Piezoelectricity is the phenomenon in which certain crystalline substances develop an electric field when subjected to pressure forces or, conversely, exhibit a mechanical deformation when subjected to an electric field. The piezoelectric affect is found only in crystals which have no center of symmetry. Examples include quartz, Rochelle salt and many synthetic polycrystalline ceramics. In the manufacture of piezoceramics, a suitable dielectric material (e.g. barium titanate or lead zirconate titanate) is first fabricated into a desired shape and then electrodes are applied to it. The piezoceramic element is then heated to an elevated temperature and subsequently cooled while in the presence of a strong direct current electric field. This process polarizes the ceramic by aligning the molecular dipoles of the ceramic in the direction of the applied field. It therefore provides it with its piezoelectric properties.
It is well known to those skilled in the art to use a piezoelectric component, such as piezoceramic, for the purpose of providing an accelerometer. In applications of this type, a weight or proof mass is attached to one side of a piezoelectric component and, as the device is subjected to acceleration, the proof mass exerts a force on the piezoelectric component and affects a preselected dimension of the piezoelectric component to either increase or decrease that dimension. In addition, since ceramics are generally much stronger in compression then in tension, they are preloaded to assure that the ceramic component is always in compression. This avoids potential damage to the piezoceramic element. As a result, strain is induced in the piezoelectric component and an electrical signal is provided that is generally representative of the acceleration exerted on the device.